Hi which resolutions better? 720P or 1080i?

Question

Hi I have 50'' Hitachi HDTV/LCD & it is 1080i resolution. My HDTV it could support down to 720P. I want to know which resolution is better to watch hi-def movies?

Answer 1

if your tv is 1080i then 720p is your best bet

if your tv is 1080p then 1080i is your best bet as your tv will scale it up and change it from interlaced to proggressive making it 1080p

Answer 2

Consider what has to happen.

Your "720p" HDTV most likely has a 1280x720 or 1366x768 pixel display panel. It "accepts" a rangle of input resolutions, including probably 480i/p, 720p and 1080i. Your display, despite accepting a 1080i input, doesn't have 1080 vertical pixels, so all input must be deinterlaced and/or scaled to fit the actual display pixels.

Deinterlacing and scaling introduce degradation (loss of information, or introduction of artifacts) in the picture. These take multiple forms -- jagged edges, noise, blurring, etc.

In essence you are therefore asking whether a 1080p/24 fps native video recorded on a Blu-ray or HD DVD disk will give a better image if output as 1080i or 720p and input to your HDTV at one or the other setting.

While you might think that 1080i "should" give a better picture because it has higher resolution than 720p, it is actually quite complex --- and almost impossible to predict.  It really comes down to the quality of the video processing.

I'll provide some reference links below, but here is a quick overview of some of the issues.

First, deinterlacing. There are different ways to deinterlace (which is always necessary on fixed pixel (e.g. LCD) display because they will only display a progressive scan image).

Some -- the cheap approach (non motion adaptive) -- throw away half the detail (in this case this would mean a 540 pixel field (half the two 540 pixel fields that made up the original 1080 pixel frame) would be scaled to fit your 720 (or 768) pixel display). In this case 720p will be superior.

Other techniques keep the full detail, unless there is motion detected, in which case they throw away half the detail for those frames (frame-based motion adaptive), and really good video processors (read, expensive) employ what is called pixel-based motion adaptive deintelacing.

Now consider scaling. To fit the incoming video to the physical display the 1080p image on the HD disk has to be scaled (See 2nd link) to fit.

If the ouput from the disk player is set to 720p the scaling takes place in the disk player and also in the HDTV (if the display is anything other than 1280x720 pixels) as the 720p signal has to be scaled to fill the 768 (or other) vertical pixels.

On the other hand, if the output is selected to be 1080i from the player the disk player must interlace the native 1080p image and the HDTV must now deinterlaced and scale the image to fit the actual display pixels.

Finally your video source can make a difference. Some do a better job than others. For example, some early Blu-ray players did a poor job of outputting 1080i, and in these cases 720p was almost always preferable.

The bottom line is either option requires multiple steps, so unless you know exactly how all your equipment processes video (and how to interpret the information) you really have to try the various options to see which works best with your equipment. Sorry if this seems like a cop-out, but it's the answer professionals would give you.

My guess is that on your HDTV 720p will give the better picture simply because of the less processing involved. But as I said ... you will have to experiment and decide.

Answer 3

Technically speaking 720p is better, but depending on the source there may not be much difference.

In essence 720p show all 720 lines at once while 1080i show 540 lines at once, the odd numbered lines (1,3,5.....) then the even numbered lines (2,4,6....). If you are sitting at a far enough distance you won't notice scan lines.....well even at the size of the lines you would have to be sitting with your face in the tv to notice scan lines.

If you are watching movies on digital cable or satellite then the native resolution is usually always 1080i....if you switch it to 720p then the picture must be converted to 1080i so it's better to just leave it at 1080i.

If it's HD DVD or Blu-ray then also leave it at 1080i.

Answer 4

ya i dont think there is such thing as 1080i tvs. that means its a 720p tv and accepts 1080i signals.....

Answer 5

Well, the larger number is higher resolution- 720p is 720 pixels, which is about 33% less than 1080.  The p stands for progressive scan, which is better than i (interlace) but the resolution difference is a big factor here.

Your Hitachi 50" at 1080i will look much more detailed, and the image will be noticeably better on stationary shots and scenes where people aren't moving around much.  So for dialog-heavy chick flicks or dramas, that's your pick.  

For fast-moving action sequences, the 720p HDTV display handles those types of movies better.